10base2 (a.k.a. thinnet) over TV coax (wrong impedance) - will it work?

Solution 1:

An impedance mismatch like that is generally a bad idea. It's not just the energy loss, but the reflections rattling all over your circuit can lead to interference. I haven't used 10base2 myself, but it sounds very sensitive to interference, and I would guess that the impedance mismatch would be a killer.

Now there are a few "redneck" ways around it.

• Try pulling through RG-58 using the 75-Ohm cable. I have done pulls here and there - it really depends on how the installation was done. There is a risk of getting stuck or tearing a cable.

• Adapt the signal over the impedance transition. There are a few ways to do this:

  • There are commercially available Impedance Matching Pads. They have an internal circuit which should do the job:

  http://www.minicircuits.com/products/MatchingPads.shtml

  • You can could try a DIY circuit, e.g.:

  http://www.ham-radio.com/k6sti/match.htm

  • Also, reflections are minimized if you gradually change the impedance of a waveguide. You could make your own cable where it gradually changes from 50 to 75 Ohm. Unfortunately, this transition cable might need to be longer than you like, and adjusting the impedance by hand is tricky.

Easiest test is to try it! (if you already have all the equipment)